CAMBRIDGE, ENGLAND—According to an Associated Press report, a new genetic analysis of 1,000-year-old walrus skulls in European museum collections suggests at that at least 80 percent of them were imported from Norse settlements in Greenland. Walrus tusks were used to produce luxury items such as ivory crucifixes, knife handles, dice, and chess sets for Europe’s medieval elite. But because museum officials have been reluctant to allow scientists to take samples of medieval artifacts for testing, the source of the ivory was unknown. James Barrett of the University of Cambridge and his colleagues found 23 walrus tusks that were still attached to pieces of skull in museum collections around Europe, and collected samples of the bones for the investigation. The researchers now think a collapse in the European market for ivory, brought on by the Black Death and other factors, may have triggered the downfall of the Norse settlements, rather than the cooler climate of the Little Ice Age, as had been previously thought. To read more about the archaeology of Greenland, go to "Letter from Greenland."